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Software QA and testing FAQ
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What is 'Software Quality Assurance'? Software QA involves the entire software development PROCESS - monitoring and improving the process, making sure that any agreed-upon standards and procedures are followed, and ensuring that problems are found and dealt with. It is oriented to 'prevention'. (See the Bookstore section's 'Software QA' category for a list of useful books on Software Quality Assurance.)
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/G.S ll3R2E5HBI0What is 'Software Testing'?
Vg,@.L(_ j Dt g0Testing involves operation of a system or application under controlled conditions and evaluating the results (eg, 'if the user is in interface A of the application while using hardware B, and does C, then D should happen'). The controlled conditions should include both normal and abnormal conditions. Testing should intentionally attempt to make things go wrong to determine if things happen when they shouldn't or things don't happen when they should. It is oriented to 'detection'. (See the Bookstore section's 'Software Testing' category for a list of useful books on Software Testing.)
O2QYt;i0Organizations vary considerably in how they assign responsibility for QA and testing. Sometimes they're the combined responsibility of one group or individual. Also common are project teams that include a mix of testers and developers who work closely together, with overall QA processes monitored by project managers. It will depend on what best fits an organization's size and business structure.
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What are some recent major computer system failures caused by software bugs?
1p\Yel G6`7a/In0Software problems in the automated baggage sorting system of a major airport in February 2008 prevented thousands of passengers from checking baggage for their flights. It was reported that the breakdown occurred during a software upgrade, despite pre-testing of the software. The system continued to have problems in subsequent months.
#O2x5ls|:Od1RD0News reports in December of 2007 indicated that significant software problems were continuing to occur in a new ERP payroll system for a large urban school system. It was believed that more than one third of employees had received incorrect paychecks at various times since the new system went live the preceding January, resulting in overpayments of $53 million, as well as underpayments. An employees' union brought a lawsuit against the school system, the cost of the ERP system was expected to rise by 40%, and the non-payroll part of the ERP system was delayed. Inadequate testing reportedly contributed to the problems. 51Testing软件测试网 RI?i Eg9}
In November of 2007 a regional government reportedly brought a multi-million dollar lawsuit against a software services vendor, claiming that the vendor 'minimized quality' in delivering software for a large criminal justice information system and the system did not meet requirements. The vendor also sued its subcontractor on the project. 51Testing软件测试网:S~KU s#K(a
In June of 2007 news reports claimed that software flaws in a popular online stock-picking contest could be used to gain an unfair advantage in pursuit of the game's large cash prizes. Outside investigators were called in and in July the contest winner was announced. Reportedly the winner had previously been in 6th place, indicating that the top 5 contestants may have been disqualified.
#] S ^2p#[U `9f4Uyh0A software problem contributed to a rail car fire in a major underground metro system in April of 2007 according to newspaper accounts. The software reportedly failed to perform as expected in detecting and preventing excess power usage in equipment on a new passenger rail car, resulting in overheating and fire in the rail car, and evacuation and shutdown of part of the system.
i[%x3O u0Tens of thousands of medical devices were recalled in March of 2007 to correct a software bug. According to news reports, the software would not reliably indicate when available power to the device was too low. 51Testing软件测试网9mc|~ [ Pm$E
A September 2006 news report indicated problems with software utilized in a state government's primary election, resulting in periodic unexpected rebooting of voter checkin machines, which were separate from the electronic voting machines, and resulted in confusion and delays at voting sites. The problem was reportedly due to insufficient testing. 51Testing软件测试网[%J0Hd{4j.kt x
In August of 2006 a U.S. government student loan service erroneously made public the personal data of as many as 21,000 borrowers on it's web site, due to a software error. The bug was fixed and the government department subsequently offered to arrange for free credit monitoring services for those affected. 51Testing软件测试网^1D3XK;B @q'M!W`
A software error reportedly resulted in overbilling of up to several thousand dollars to each of 11,000 customers of a major telecommunications company in June of 2006. It was reported that the software bug was fixed within days, but that correcting the billing errors would take much longer. 51Testing软件测试网 bP%{E3M6D6H `M
News reports in May of 2006 described a multi-million dollar lawsuit settlement paid by a healthcare software vendor to one of its customers. It was reported that the customer claimed there were problems with the software they had contracted for, including poor integration of software modules, and problems that resulted in missing or incorrect data used by medical personnel.
;Or|5z x;^@!m0In early 2006 problems in a government's financial monitoring software resulted in incorrect election candidate financial reports being made available to the public. The government's election finance reporting web site had to be shut down until the software was repaired.
3ZC:f7Z)N1c!h Cc5G0Trading on a major Asian stock exchange was brought to a halt in November of 2005, reportedly due to an error in a system software upgrade. The problem was rectified and trading resumed later the same day. 51Testing软件测试网[6x;n/m"M2B&\
A May 2005 newspaper article reported that a major hybrid car manufacturer had to install a software fix on 20,000 vehicles due to problems with invalid engine warning lights and occasional stalling. In the article, an automotive software specialist indicated that the automobile industry spends $2 billion to $3 billion per year fixing software problems.
3bG P7[M sw z+wE0Media reports in January of 2005 detailed severe problems with a $170 million high-profile U.S. government IT systems project. Software testing was one of the five major problem areas according to a report of the commission reviewing the project. In March of 2005 it was decided to scrap the entire project.
(^,e&tJi U$[N0In July 2004 newspapers reported that a new government welfare management system in Canada costing several hundred million dollars was unable to handle a simple benefits rate increase after being put into live operation. Reportedly the original contract allowed for only 6 weeks of acceptance testing and the system was never tested for its ability to handle a rate increase.
e7Y-['uvx4b+n,E0Millions of bank accounts were impacted by errors due to installation of inadequately tested software code in the transaction processing system of a major North American bank, according to mid-2004 news reports. Articles about the incident stated that it took two weeks to fix all the resulting errors, that additional problems resulted when the incident drew a large number of e-mail phishing attacks against the bank's customers, and that the total cost of the incident could exceed $100 million. 51Testing软件测试网N&_+AY;I O4X*XI
A bug in site management software utilized by companies with a significant percentage of worldwide web traffic was reported in May of 2004. The bug resulted in performance problems for many of the sites simultaneously and required disabling of the software until the bug was fixed.
0`&dZ qKIIx0According to news reports in April of 2004, a software bug was determined to be a major contributor to the 2003 Northeast blackout, the worst power system failure in North American history. The failure involved loss of electrical power to 50 million customers, forced shutdown of 100 power plants, and economic losses estimated at $6 billion. The bug was reportedly in one utility company's vendor-supplied power monitoring and management system, which was unable to correctly handle and report on an unusual confluence of initially localized events. The error was found and corrected after examining millions of lines of code. 51Testing软件测试网N[ {{_1b%nG}
In early 2004, news reports revealed the intentional use of a software bug as a counter-espionage tool. According to the report, in the early 1980's one nation surreptitiously allowed a hostile nation's espionage service to steal a version of sophisticated industrial software that had intentionally-added flaws. This eventually resulted in major industrial disruption in the country that used the stolen flawed software. 51Testing软件测试网Fx!B)vUZ T
A major U.S. retailer was reportedly hit with a large government fine in October of 2003 due to web site errors that enabled customers to view one anothers' online orders. 51Testing软件测试网'qfNbo}
News stories in the fall of 2003 stated that a manufacturing company recalled all their transportation products in order to fix a software problem causing instability in certain circumstances. The company found and reported the bug itself and initiated the recall procedure in which a software upgrade fixed the problems.
cM1|*yk6H5b0In August of 2003 a U.S. court ruled that a lawsuit against a large online brokerage company could proceed; the lawsuit reportedly involved claims that the company was not fixing system problems that sometimes resulted in failed stock trades, based on the experiences of 4 plaintiffs during an 8-month period. A previous lower court's ruling that "...six miscues out of more than 400 trades does not indicate negligence." was invalidated.
?P P5jw&]0In April of 2003 it was announced that a large student loan company in the U.S. made a software error in calculating the monthly payments on 800,000 loans. Although borrowers were to be notified of an increase in their required payments, the company will still reportedly lose $8 million in interest. The error was uncovered when borrowers began reporting inconsistencies in their bills.
t)@|GB0News reports in February of 2003 revealed that the U.S. Treasury Department mailed 50,000 Social Security checks without any beneficiary names. A spokesperson indicated that the missing names were due to an error in a software change. Replacement checks were subsequently mailed out with the problem corrected, and recipients were then able to cash their Social Security checks.
#K FhH*c Y}5Y0In March of 2002 it was reported that software bugs in Britain's national tax system resulted in more than 100,000 erroneous tax overcharges. The problem was partly attributed to the difficulty of testing the integration of multiple systems. 51Testing软件测试网:fKg F(S q JM2A!^
A newspaper columnist reported in July 2001 that a serious flaw was found in off-the-shelf software that had long been used in systems for tracking certain U.S. nuclear materials. The same software had been recently donated to another country to be used in tracking their own nuclear materials, and it was not until scientists in that country discovered the problem, and shared the information, that U.S. officials became aware of the problems. 51Testing软件测试网/A` @yHn
According to newspaper stories in mid-2001, a major systems development contractor was fired and sued over problems with a large retirement plan management system. According to the reports, the client claimed that system deliveries were late, the software had excessive defects, and it caused other systems to crash.
!p Td:n }2~0In January of 2001 newspapers reported that a major European railroad was hit by the aftereffects of the Y2K bug. The company found that many of their newer trains would not run due to their inability to recognize the date '31/12/2000'; the trains were started by altering the control system's date settings.
J xH3I&z(^6l0News reports in September of 2000 told of a software vendor settling a lawsuit with a large mortgage lender; the vendor had reportedly delivered an online mortgage processing system that did not meet specifications, was delivered late, and didn't work. 51Testing软件测试网4h*c UP8r's,s
In early 2000, major problems were reported with a new computer system in a large suburban U.S. public school district with 100,000+ students; problems included 10,000 erroneous report cards and students left stranded by failed class registration systems; the district's CIO was fired. The school district decided to reinstate it's original 25-year old system for at least a year until the bugs were worked out of the new system by the software vendors. 51Testing软件测试网z/RTvB{ty'~
A review board concluded that the NASA Mars Polar Lander failed in December 1999 due to software problems that caused improper functioning of retro rockets utilized by the Lander as it entered the Martian atmosphere. 51Testing软件测试网 w(~7la%T`,P(WZX
In October of 1999 the $125 million NASA Mars Climate Orbiter spacecraft was believed to be lost in space due to a simple data conversion error. It was determined that spacecraft software used certain data in English units that should have been in metric units. Among other tasks, the orbiter was to serve as a communications relay for the Mars Polar Lander mission, which failed for unknown reasons in December 1999. Several investigating panels were convened to determine the process failures that allowed the error to go undetected. 51Testing软件测试网 KIK B*H7Xf)GN
Bugs in software supporting a large commercial high-speed data network affected 70,000 business customers over a period of 8 days in August of 1999. Among those affected was the electronic trading system of the largest U.S. futures exchange, which was shut down for most of a week as a result of the outages. 51Testing软件测试网x8v H2TE
In April of 1999 a software bug caused the failure of a $1.2 billion U.S. military satellite launch, the costliest unmanned accident in the history of Cape Canaveral launches. The failure was the latest in a string of launch failures, triggering a complete military and industry review of U.S. space launch programs, including software integration and testing processes. Congressional oversight hearings were requested. 51Testing软件测试网.V eG _S+y
A small town in Illinois in the U.S. received an unusually large monthly electric bill of $7 million in March of 1999. This was about 700 times larger than its normal bill. It turned out to be due to bugs in new software that had been purchased by the local power company to deal with Y2K software issues. 51Testing软件测试网)rqx l5v T,q P a q@
In early 1999 a major computer game company recalled all copies of a popular new product due to software problems. The company made a public apology for releasing a product before it was ready.
P0G8` mT1[0The computer system of a major online U.S. stock trading service failed during trading hours several times over a period of days in February of 1999 according to nationwide news reports. The problem was reportedly due to bugs in a software upgrade intended to speed online trade confirmations.
(S [,j/fe-U L0In April of 1998 a major U.S. data communications network failed for 24 hours, crippling a large part of some U.S. credit card transaction authorization systems as well as other large U.S. bank, retail, and government data systems. The cause was eventually traced to a software bug.
uUBT H ET0January 1998 news reports told of software problems at a major U.S. telecommunications company that resulted in no charges for long distance calls for a month for 400,000 customers. The problem went undetected until customers called up with questions about their bills. 51Testing软件测试网6X[ _;W0Q0B
In November of 1997 the stock of a major health industry company dropped 60% due to reports of failures in computer billing systems, problems with a large database conversion, and inadequate software testing. It was reported that more than $100,000,000 in receivables had to be written off and that multi-million dollar fines were levied on the company by government agencies.
C+[({&p e"~0A retail store chain filed suit in August of 1997 against a transaction processing system vendor (not a credit card company) due to the software's inability to handle credit cards with year 2000 expiration dates.
3w.W9I1B g0P+C}!E!O0In August of 1997 one of the leading consumer credit reporting companies reportedly shut down their new public web site after less than two days of operation due to software problems. The new site allowed web site visitors instant access, for a small fee, to their personal credit reports. However, a number of initial users ended up viewing each others' reports instead of their own, resulting in irate customers and nationwide publicity. The problem was attributed to "...unexpectedly high demand from consumers and faulty software that routed the files to the wrong computers."
_t g.fh I+z/u [0In November of 1996, newspapers reported that software bugs caused the 411 telephone information system of one of the U.S. RBOC's to fail for most of a day. Most of the 2000 operators had to search through phone books instead of using their 13,000,000-listing database. The bugs were introduced by new software modifications and the problem software had been installed on both the production and backup systems. A spokesman for the software vendor reportedly stated that 'It had nothing to do with the integrity of the software. It was human error.' 51Testing软件测试网h;\4r7i3[ J6R/~;@
On June 4 1996 the first flight of the European Space Agency's new Ariane 5 rocket failed shortly after launching, resulting in an estimated uninsured loss of a half billion dollars. It was reportedly due to the lack of exception handling of a floating-point error in a conversion from a 64-bit integer to a 16-bit signed integer.
.D~gX;b E ~0Software bugs caused the bank accounts of 823 customers of a major U.S. bank to be credited with $924,844,208.32 each in May of 1996, according to newspaper reports. The American Bankers Association claimed it was the largest such error in banking history. A bank spokesman said the programming errors were corrected and all funds were recovered. 51Testing软件测试网n D$|:k0ZS c
On January 1 1984 all computers produced by one of the leading minicomputer makers of the time reportedly failed worldwide. The cause was claimed to be a leap year bug in a date handling function utilized in deletion of temporary operating system files. Technicians throughout the world worked for several days to clear up the problem. It was also reported that the same bug affected many of the same computers four years later.
Pr"pA H4K Fb sG0Software bugs in a Soviet early-warning monitoring system nearly brought on nuclear war in 1983, according to news reports in early 1999. The software was supposed to filter out false missile detections caused by Soviet satellites picking up sunlight reflections off cloud-tops, but failed to do so. Disaster was averted when a Soviet commander, based on what he said was a '...funny feeling in my gut', decided the apparent missile attack was a false alarm. The filtering software code was rewritten.
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n f+q)y y:p oDF8C F |0Does every software project need testers? 51Testing软件测试网l'MDX }
While all projects will benefit from testing, some projects may not require independent test staff to succeed. 51Testing软件测试网wc3B&H U/|q y
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Which projects may not need independent test staff? The answer depends on the size and context of the project, the risks, the development methodology, the skill and experience of the developers, and other factors. For instance, if the project is a short-term, small, low risk project, with highly experienced programmers utilizing thorough unit testing or test-first development, then test engineers may not be required for the project to succeed.
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In some cases an IT organization may be too small or new to have a testing staff even if the situation calls for it. In these circumstances it may be appropriate to instead use contractors or outsourcing, or adjust the project management and development approach (by switching to more senior developers and agile test-first development, for example). Inexperienced managers sometimes gamble on the success of a project by skipping thorough testing or having programmers do post-development functional testing of their own work, a decidedly high risk gamble.
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For non-trivial-size projects or projects with non-trivial risks, a testing staff is usually necessary. As in any business, the use of personnel with specialized skills enhances an organization's ability to be successful in large, complex, or difficult tasks. It allows for both a) deeper and stronger skills and b) the contribution of differing perspectives. For example, programmers typically have the perspective of 'what are the technical issues in making this functionality work?'. A test engineer typically has the perspective of 'what might go wrong with this functionality, and how can we ensure it meets expectations?'. Technical people who can be highly effective in approaching tasks from both of those perspectives are rare, which is why, sooner or later, organizations bring in test specialists. 51Testing软件测试网7L){ L F^!a5B
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.Z X\ V8eV0Why does software have bugs?
E#vaz;@0miscommunication or no communication - as to specifics of what an application should or shouldn't do (the application's requirements). 51Testing软件测试网0P8l(_%Z'q I5D-u
software complexity - the complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development. Multi-tier distributed systems, applications utilizing mutliple local and remote web services applications, data communications, enormous relational databases, security complexities, and sheer size of applications have all contributed to the exponential growth in software/system complexity.
P^1M[ R)S1W0programming errors - programmers, like anyone else, can make mistakes.
$^,e(n#y G U0changing requirements (whether documented or undocumented) - the end-user may not understand the effects of changes, or may understand and request them anyway - redesign, rescheduling of engineers, effects on other projects, work already completed that may have to be redone or thrown out, hardware requirements that may be affected, etc. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of coordinating changes may result in errors. Enthusiasm of engineering staff may be affected. In some fast-changing business environments, continuously modified requirements may be a fact of life. In this case, management must understand the resulting risks, and QA and test engineers must adapt and plan for continuous extensive testing to keep the inevitable bugs from running out of control - see 'What can be done if requirements are changing continuously?' in the LFAQ. Also see information about 'agile' approaches such as XP, in Part 2 of the FAQ. 51Testing软件测试网+OP"[8J$|:V An5F
time pressures - scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.
hc j3EWE#Y0egos - people prefer to say things like:
7Rh {:zwkwC\0 'no problem'
X jSC px:i RK"Mr0 'piece of cake'51Testing软件测试网(FH*M$WO%MF8L\
'I can whip that out in a few hours'
.g-`\| ]+f0 'it should be easy to update that old code'51Testing软件测试网+G~!bF!~S
~ IH0q W3Yj9y0 instead of:51Testing软件测试网 ciA)l3U2s fX9r
'that adds a lot of complexity and we could end up51Testing软件测试网6UF1fQP*a0W
making a lot of mistakes'
-d Ot1at3I6F2L |(d Y0 'we have no idea if we can do that; we'll wing it'51Testing软件测试网8m5ey(hp$D t C @
'I can't estimate how long it will take, until I51Testing软件测试网UVT V5W {^0M
take a close look at it'
&g ~D_!K b-X0 'we can't figure out what that old spaghetti code51Testing软件测试网Bvj'll*T
did in the first place'51Testing软件测试网;I _9x.KXA
k*g [+H*H'q0 If there are too many unrealistic 'no problem's', the
ol mCh?6LE&C]0 result is bugs.51Testing软件测试网0L'`"H+u}+ox&W
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poorly documented code - it's tough to maintain and modify code that is badly written or poorly documented; the result is bugs. In many organizations management provides no incentive for programmers to document their code or write clear, understandable, maintainable code. In fact, it's usually the opposite: they get points mostly for quickly turning out code, and there's job security if nobody else can understand it ('if it was hard to write, it should be hard to read'). 51Testing软件测试网 U'^x6lB?;a$p
software development tools - visual tools, class libraries, compilers, scrīpting tools, etc. often introduce their own bugs or are poorly documented, resulting in added bugs.
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How can new Software QA processes be introduced in an existing organization? 51Testing软件测试网 ?7?:mT gu F
A lot depends on the size of the organization and the risks involved. For large organizations with high-risk (in terms of lives or property) projects, serious management buy-in is required and a formalized QA process is necessary. 51Testing软件测试网(M({ U2gK,m om
Where the risk is lower, management and organizational buy-in and QA implementation may be a slower, step-at-a-time process. QA processes should be balanced with productivity so as to keep bureaucracy from getting out of hand. 51Testing软件测试网YC$@d V%FP#M
For small groups or projects, a more ad-hoc process may be appropriate, depending on the type of customers and projects. A lot will depend on team leads or managers, feedback to developers, and ensuring adequate communications among customers, managers, developers, and testers. 51Testing软件测试网+||E Y:G,{%M-f b+_
The most value for effort will often be in (a) requirements management processes, with a goal of clear, complete, testable requirement specifications embodied in requirements or design documentation, or in 'agile'-type environments extensive continuous coordination with end-users, (b) design inspections and code inspections, and (c) post-mortems/retrospectives. 51Testing软件测试网T `Vs%t
Other possibilities include incremental self-managed team approaches such as 'Kaizen' methods of continuous process improvement, the Deming-Shewhart Plan-Do-Check-Act cycle, and others. 51Testing软件测试网GZ!iT J:t
Also see 'How can QA processes be implemented without reducing productivity?' in the LFAQ section.
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kA/Xx'wEL/JU0(See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.) 51Testing软件测试网o)z {+^ X4n9V
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2B4ZZM aX3U `m0What is verification? validation? 51Testing软件测试网*U i2T o YhkW P
Verification typically involves reviews and meetings to evaluate documents, plans, code, requirements, and specifications. This can be done with checklists, issues lists, walkthroughs, and inspection meetings. Validation typically involves actual testing and takes place after verifications are completed. The term 'IV & V' refers to Independent Verification and Validation.
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|/f*Jh'o D0M @|!le0What is a 'walkthrough'? 51Testing软件测试网#n0H:nq|(`0ra
A 'walkthrough' is an informal meeting for evaluation or informational purposes. Little or no preparation is usually required. 51Testing软件测试网6T#MN L)r(c
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51Testing软件测试网\.W\/g.oPbF
What's an 'inspection'?
R{w*V2V#\0An inspection is more formalized than a 'walkthrough', typically with 3-8 people including a moderator, reader, and a recorder to take notes. The subject of the inspection is typically a document such as a requirements spec or a test plan, and the purpose is to find problems and see what's missing, not to fix anything. Attendees should prepare for this type of meeting by reading thru the document; most problems will be found during this preparation. The result of the inspection meeting should be a written report. Thorough preparation for inspections is difficult, painstaking work, but is one of the most cost effective methods of ensuring quality. Employees who are most skilled at inspections are like the 'eldest brother' in the parable in 'Why is it often hard for organizations to get serious about quality assurance?'. Their skill may have low visibility but they are extremely valuable to any software development organization, since bug prevention is far more cost-effective than bug detection. 51Testing软件测试网#MX$| x&N {e
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Si[v7n5^/O$@!q051Testing软件测试网*j xB$UOG9A"Am4Q
What kinds of testing should be considered? 51Testing软件测试网9`lhE F^d@
Black box testing - not based on any knowledge of internal design or code. Tests are based on requirements and functionality. 51Testing软件测试网(@:H5t L#X8q @U4v%m
White box testing - based on knowledge of the internal logic of an application's code. Tests are based on coverage of code statements, branches, paths, conditions. 51Testing软件测试网g _ Z [1jk~8j
unit testing - the most 'micro' scale of testing; to test particular functions or code modules. Typically done by the programmer and not by testers, as it requires detailed knowledge of the internal program design and code. Not always easily done unless the application has a well-designed architecture with tight code; may require developing test driver modules or test harnesses. 51Testing软件测试网,Gq'[._ U z3R#J1E
incremental integration testing - continuous testing of an application as new functionality is added; requires that various aspects of an application's functionality be independent enough to work separately before all parts of the program are completed, or that test drivers be developed as needed; done by programmers or by testers. 51Testing软件测试网J0Q W3Fti
integration testing - testing of combined parts of an application to determine if they function together correctly. The 'parts' can be code modules, individual applications, client and server applications on a network, etc. This type of testing is especially relevant to client/server and distributed systems. 51Testing软件测试网 FL$pgE;R
functional testing - black-box type testing geared to functional requirements of an application; this type of testing should be done by testers. This doesn't mean that the programmers shouldn't check that their code works before releasing it (which of course applies to any stage of testing.) 51Testing软件测试网3u RL+w6[0pO
system testing - black-box type testing that is based on overall requirements specifications; covers all combined parts of a system. 51Testing软件测试网(Y9l O tt"V x9g0f-?
end-to-end testing - similar to system testing; the 'macro' end of the test scale; involves testing of a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.
"k `F!j*}n0sanity testing or smoke testing - typically an initial testing effort to determine if a new software version is performing well enough to accept it for a major testing effort. For example, if the new software is crashing systems every 5 minutes, bogging down systems to a crawl, or corrupting databases, the software may not be in a 'sane' enough condition to warrant further testing in its current state.
Ui(U:B4C:F Y`7S0regression testing - re-testing after fixes or modifications of the software or its environment. It can be difficult to determine how much re-testing is needed, especially near the end of the development cycle. Automated testing tools can be especially useful for this type of testing.
._+c xi-v&e0acceptance testing - final testing based on specifications of the end-user or customer, or based on use by end-users/customers over some limited period of time. 51Testing软件测试网 zF5Jl9I X
load testing - testing an application under heavy loads, such as testing of a web site under a range of loads to determine at what point the system's response time degrades or fails.
^&\9b2M1{0stress testing - term often used interchangeably with 'load' and 'performance' testing. Also used to describe such tests as system functional testing while under unusually heavy loads, heavy repetition of certain actions or inputs, input of large numerical values, large complex queries to a database system, etc.
X2n#\ { WOJ0performance testing - term often used interchangeably with 'stress' and 'load' testing. Ideally 'performance' testing (and any other 'type' of testing) is defined in requirements documentation or QA or Test Plans.
:m | sP;yu0usability testing - testing for 'user-friendliness'. Clearly this is subjective, and will depend on the targeted end-user or customer. User interviews, surveys, video recording of user sessions, and other techniques can be used. Programmers and testers are usually not appropriate as usability testers.
C)weFIsT b0install/uninstall testing - testing of full, partial, or upgrade install/uninstall processes. 51Testing软件测试网h1^6P|Of T7Z$F
recovery testing - testing how well a system recovers from crashes, hardware failures, or other catastrophic problems.
'[4Y u!\;j+Q@0failover testing - typically used interchangeably with 'recovery testing' 51Testing软件测试网X+hD7K4ql,n k |
security testing - testing how well the system protects against unauthorized internal or external access, willful damage, etc; may require sophisticated testing techniques.
/C F-t:R x6zs"{0compatability testing - testing how well software performs in a particular hardware/software/operating system/network/etc. environment. 51Testing软件测试网:I$}`5G(H7y1w
exploratory testing - often taken to mean a creative, informal software test that is not based on formal test plans or test cases; testers may be learning the software as they test it. 51Testing软件测试网u? g n U5I
ad-hoc testing - similar to exploratory testing, but often taken to mean that the testers have significant understanding of the software before testing it. 51Testing软件测试网(f BAs J LB!C l a
context-driven testing - testing driven by an understanding of the environment, culture, and intended use of software. For example, the testing approach for life-critical medical equipment software would be completely different than that for a low-cost computer game.
.wh\`:E0i\\R| u0user acceptance testing - determining if software is satisfactory to an end-user or customer. 51Testing软件测试网H k"pQ Z/V L+C b0`:g;?
comparison testing - comparing software weaknesses and strengths to competing products.
0r;Z`2w"Ku N/Q0alpha testing - testing of an application when development is nearing completion; minor design changes may still be made as a result of such testing. Typically done by end-users or others, not by programmers or testers.
@*}"k mT ~Ec%G0beta testing - testing when development and testing are essentially completed and final bugs and problems need to be found before final release. Typically done by end-users or others, not by programmers or testers. 51Testing软件测试网"}6y v!]f3^%jM @
mutation testing - a method for determining if a set of test data or test cases is useful, by deliberately introducing various code changes ('bugs') and retesting with the original test data/cases to determine if the 'bugs' are detected. Proper implementation requires large computational resources.
9Z n"y1A1o i0(See the Bookstore section's 'Software Testing' category for useful books on Software Testing.) 51Testing软件测试网9l.V3A)t4k [8j9l5c
51Testing软件测试网:K'T4He+WB ]
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51Testing软件测试网8?-da3w&OB/N
What are 5 common problems in the software development process?
:yI6VX q0poor requirements - if requirements are unclear, incomplete, too general, and not testable, there will be problems. 51Testing软件测试网+u.Z? n$L y8]\
unrealistic schedule - if too much work is crammed in too little time, problems are inevitable.
@]$R C)];U0inadequate testing - no one will know whether or not the program is any good until the customer complains or systems crash.
{j4g&D3O2vH0featuritis - requests to pile on new features after development is underway; extremely common. 51Testing软件测试网1cFy[.|`.C3yKF
miscommunication - if developers don't know what's needed or customer's have erroneous expectations, problems can be expected.
a XBj$E%@9}#a3?r0(See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.) 51Testing软件测试网.x#_$].hay4k {
%U4b(Dad.Q @W0Return to top of this page's FAQ list 51Testing软件测试网i3u3M+z3Y s,D){
51Testing软件测试网d [b Aa$X2n~
What are 5 common solutions to software development problems?
uLA2@CD ]6ns0solid requirements - clear, complete, detailed, cohesive, attainable, testable requirements that are agreed to by all players. In 'agile'-type environments, continuous close coordination with customers/end-users is necessary to ensure that changing/emerging requirements are understood.
4p9l \!uy(O9U9C0realistic schedules - allow adequate time for planning, design, testing, bug fixing, re-testing, changes, and documentation; personnel should be able to complete the project without burning out.
dqib @$`x%~Z0adequate testing - start testing early on, re-test after fixes or changes, plan for adequate time for testing and bug-fixing. 'Early' testing could include static code analysis/testing, test-first development, unit testing by developers, built-in testing and diagnostic capabilities, automated post-build testing, etc. 51Testing软件测试网t4T2t'^lF0D:{b
stick to initial requirements where feasible - be prepared to defend against excessive changes and additions once development has begun, and be prepared to explain consequences. If changes are necessary, they should be adequately reflected in related schedule changes. If possible, work closely with customers/end-users to manage expectations. In 'agile'-type environments, initial requirements may be expected to change significantly, requiring that true agile processes be in place. 51Testing软件测试网 y2mT.U x(Ia5np
communication - require walkthroughs and inspections when appropriate; make extensive use of group communication tools - groupware, wiki's, bug-tracking tools and change management tools, intranet capabilities, etc.; ensure that information/documentation is available and up-to-date - preferably electronic, not paper; promote teamwork and cooperation; use protoypes and/or continuous communication with end-users if possible to clarify expectations. 51Testing软件测试网.e5If5M)d V j9F5v6hf7?
(See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.) 51Testing软件测试网,v2I|5?j ~
2~2Eh&Rdf0Return to top of this page's FAQ list 51Testing软件测试网+@4y^$D`t^,y
"U$J jg:^ Nl6tY{2?#@0What is software 'quality'? 51Testing软件测试网6Tw(V3aO {!}b {
Quality software is reasonably bug-free, delivered on time and within budget, meets requirements and/or expectations, and is maintainable. However, quality is obviously a subjective term. It will depend on who the 'customer' is and their overall influence in the scheme of things. A wide-angle view of the 'customers' of a software development project might include end-users, customer acceptance testers, customer contract officers, customer management, the development organization's management/accountants/testers/salespeople, future software maintenance engineers, stockholders, magazine columnists, etc. Each type of 'customer' will have their own slant on 'quality' - the accounting department might define quality in terms of profits while an end-user might define quality as user-friendly and bug-free. (See the Bookstore section's 'Software QA' category for useful books with more information.) 51Testing软件测试网 gM f*~ `
1f4L H Q8P2k0Return to top of this page's FAQ list 51Testing软件测试网1\X.u8A7U-MI p0PE
X mJ7k3@ C b7p k0What is 'good code'?
)D UC*gg;du$A M0'Good code' is code that works, is reasonably bug free, and is readable and maintainable. Some organizations have coding 'standards' that all developers are supposed to adhere to, but everyone has different ideas about what's best, or what is too many or too few rules. There are also various theories and metrics, such as McCabe Complexity metrics. It should be kept in mind that excessive use of standards and rules can stifle productivity and creativity. 'Peer reviews', 'buddy checks' pair programming, code analysis tools, etc. can be used to check for problems and enforce standards.
z#^ cq m2NFY9tJED0For example, in C/C++ coding, here are some typical ideas to consider in setting rules/standards; these may or may not apply to a particular situation:
A1_+G1TFIq0minimize or eliminate use of global variables. 51Testing软件测试网*w U cX&U J
use descrīptive function and method names - use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descrīptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
V"a#uPqfc0use descrīptive variable names - use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descrīptive (use of more than 20 characters is not out of line); be consistent in naming conventions. 51Testing软件测试网6X Y#n!CS
function and method sizes should be minimized; less than 100 lines of code is good, less than 50 lines is preferable. 51Testing软件测试网SMFm.iN X-g4_+W
function descrīptions should be clearly spelled out in comments preceding a function's code.
)B~EiS0organize code for readability. 51Testing软件测试网&M ngkd"d@
use whitespace generously - vertically and horizontally 51Testing软件测试网2? j1U U@
each line of code should contain 70 characters max. 51Testing软件测试网P'vd*pWV;@
one code statement per line.
x F ACz(n%a0coding style should be consistent throught a program (eg, use of brackets, indentations, naming conventions, etc.)
XJ)eJE d3i4V0in adding comments, err on the side of too many rather than too few comments; a common rule of thumb is that there should be at least as many lines of comments (including header blocks) as lines of code.
A7AA#do'\Zj4e$R0no matter how small, an application should include documentaion of the overall program function and flow (even a few paragraphs is better than nothing); or if possible a separate flow chart and detailed program documentation. 51Testing软件测试网 G!j~-Q;m aw
make extensive use of error handling procedures and status and error logging. 51Testing软件测试网a/p p X*Rw
for C++, to minimize complexity and increase maintainability, avoid too many levels of inheritance in class heirarchies (relative to the size and complexity of the application). Minimize use of multiple inheritance, and minimize use of operator overloading (note that the Java programming language eliminates multiple inheritance and operator overloading.) 51Testing软件测试网 G `(T0}V9^#c d{8[L
for C++, keep class methods small, less than 50 lines of code per method is preferable.
`h]"XvL now0for C++, make liberal use of exception handlers 51Testing软件测试网 U5v c0cJ*_
!D ^5P3e3Y6U,] }0Return to top of this page's FAQ list 51Testing软件测试网E LD.v x||:~Y
51Testing软件测试网%l ID6_)o/R?
What is 'good design'? 51Testing软件测试网H;KH0|`5bp&e%Dk
'Design' could refer to many things, but often refers to 'functional design' or 'internal design'. Good internal design is indicated by software code whose overall structure is clear, understandable, easily modifiable, and maintainable; is robust with sufficient error-handling and status logging capability; and works correctly when implemented. Good functional design is indicated by an application whose functionality can be traced back to customer and end-user requirements. (See further discussion of functional and internal design in 'What's the big deal about requirements?' in FAQ #2.) For programs that have a user interface, it's often a good idea to assume that the end user will have little computer knowledge and may not read a user manual or even the on-line help; some common rules-of-thumb include:
UY'?6F0F0W$Y0the program should act in a way that least surprises the user 51Testing软件测试网%x MuMt*ny8O:}
it should always be evident to the user what can be done next and how to exit 51Testing软件测试网NxoP-b Mc:w(d
the program shouldn't let the users do something stupid without warning them.
(d?Li3b"[051Testing软件测试网)C{,vX8?:o2aSb
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*j3\F o _ F~9H d|+l2P0What is SEI? CMM? CMMI? ISO? IEEE? ANSI? Will it help?
+}?P{&Y E ~.{0SEI = 'Software Engineering Institute' at Carnegie-Mellon University; initiated by the U.S. Defense Department to help improve software development processes.
I%|?"~_$MW0CMM = 'Capability Maturity Model', now called the CMMI ('Capability Maturity Model Integration'), developed by the SEI. It's a model of 5 levels of process 'maturity' that determine effectiveness in delivering quality software. It is geared to large organizations such as large U.S. Defense Department contractors. However, many of the QA processes involved are appropriate to any organization, and if reasonably applied can be helpful. Organizations can receive CMMI ratings by undergoing assessments by qualified auditors.
2tG)H d:v&}.yt E0 Level 1 - characterized by chaos, periodic panics, and heroic51Testing软件测试网 a#q(UK1F4hb#Q6m'M
efforts required by individuals to successfully51Testing软件测试网2x0j] }!},m A#X.s {E
complete projects. Few if any processes in place;
;fF x5lS+w7@ f.FF0 successes may not be repeatable.
.S n q3[W(IX6rhcjp5{051Testing软件测试网M:Rr Vd1OT8q
Level 2 - software project tracking, requirements management,51Testing软件测试网@X8s*r$Z0O8i
realistic planning, and configuration management
H9U;Ip;U2@f0 processes are in place; successful practices can
'F(_%b @$x9G;l0 be repeated.51Testing软件测试网oLJ vVS5]*?[
q}m|%r1R C1Fj0 Level 3 - standard software development and maintenance processes
4L;d6E&H k$_:A0 are integrated throughout an organization; a Software
vn1l `Gw@ b5c*@0 Engineering Process Group is is in place to oversee51Testing软件测试网-X.tQ9v/Ur.|
software processes, and training programs are used to
.F2X#DH6Su+J(m0 ensure understanding and compliance.51Testing软件测试网XE4B:\n
#f2G t.UV1T0 Level 4 - metrics are used to track productivity, processes,51Testing软件测试网/i~Bn [1I$~bc
and products. Project performance is predictable,51Testing软件测试网 z!w"T PY%y d8? B X
and quality is consistently high.
4KR'z2y"bcY9y051Testing软件测试网f(I5[s'd U d
Level 5 - the focus is on continouous process improvement. The
q$eJ*P1}+j`0 impact of new processes and technologies can be
;P(F7I~~id S0 predicted and effectively implemented when required.51Testing软件测试网r)P n3J.Q'p G Cl4d\
b+kN!q En k0
1aB v/Z&K'@*F%s0 Perspective on CMM ratings: During 1997-2001, 1018 organizations51Testing软件测试网+|d)v_[(r&o Z
were assessed. Of those, 27% were rated at Level 1, 39% at 2,51Testing软件测试网.A0i7b dA
23% at 3, 6% at 4, and 5% at 5. (For ratings during the period 51Testing软件测试网$X$i B)n iM'K
1992-96, 62% were at Level 1, 23% at 2, 13% at 3, 2% at 4, and 51Testing软件测试网2@EH#N,N$|
0.4% at 5.) The median size of organizations was 100 software
E7{4aY_ nM0 engineering/maintenance personnel; 32% of organizations were
,` I+W)^0\5n xM0 U.S. federal contractors or agencies. For those rated at
2C{2s z Mq9fT0 Level 1, the most problematical key process area was in
P0J^(gX^bVH0 Software Quality Assurance.51Testing软件测试网2d9} BiH
NiG j ` [ XD/^0ISO = 'International Organisation for Standardization' - The ISO 9001:2000 standard (which replaces the previous standard of 1994) concerns quality systems that are assessed by outside auditors, and it applies to many kinds of production and manufacturing organizations, not just software. It covers documentation, design, development, production, testing, installation, servicing, and other processes. The full set of standards consists of: (a)Q9001-2000 - Quality Management Systems: Requirements; (b)Q9000-2000 - Quality Management Systems: Fundamentals and Vocabulary; (c)Q9004-2000 - Quality Management Systems: Guidelines for Performance Improvements. To be ISO 9001 certified, a third-party auditor assesses an organization, and certification is typically good for about 3 years, after which a complete reassessment is required. Note that ISO certification does not necessarily indicate quality products - it indicates only that documented processes are followed. Also see http://www.iso.org/ for the latest information. In the U.S. the standards can be purchased via the ASQ web site at http://www.asq.org/quality-press/ 51Testing软件测试网 LZ%]0X$H:uq v
ISO 9126 defines six high level quality characteristics that can be used in software evaluation. It includes functionality, reliability, usability, efficiency, maintainability, and portability.
] u_5V%b/} ]0IEEE = 'Institute of Electrical and Electronics Engineers' - among other things, creates standards such as 'IEEE Standard for Software Test Documentation' (IEEE/ANSI Standard 829), 'IEEE Standard of Software Unit Testing (IEEE/ANSI Standard 1008), 'IEEE Standard for Software Quality Assurance Plans' (IEEE/ANSI Standard 730), and others.
3C;s*P0L}1@0ANSI = 'American National Standards Institute', the primary industrial standards body in the U.S.; publishes some software-related standards in conjunction with the IEEE and ASQ (American Society for Quality).
@|*y8B3i!X$J}"v"MN0Other software development/IT management process assessment methods besides CMMI and ISO 9000 include SPICE, Trillium, TickIT, Bootstrap, ITIL, MOF, and CobiT. 51Testing软件测试网 N HH!U Iu$Z f,o3\
See the 'Other Resources' section for further information available on the web.
;G Y ? a ?y1n/h+f8_051Testing软件测试网@ U[0F2\
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.[ hP } Z'L9j0What is the 'software life cycle'? 51Testing软件测试网 kB7q+Qmvt W D Q
The life cycle begins when an application is first conceived and ends when it is no longer in use. It includes aspects such as initial concept, requirements analysis, functional design, internal design, documentation planning, test planning, coding, document preparation, integration, testing, maintenance, updates, retesting, phase-out, and other aspects. (See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.)
e lO EU]S0
J-r$h(|\.S0
p9Q'|3o m0
+Q i}'H@ Ow {0Return to top of this page's FAQ list 51Testing软件测试网{ ?zSI#rjO Y"auD
/G.S ll3R2E5HBI0What is 'Software Testing'?
Vg,@.L(_ j Dt g0Testing involves operation of a system or application under controlled conditions and evaluating the results (eg, 'if the user is in interface A of the application while using hardware B, and does C, then D should happen'). The controlled conditions should include both normal and abnormal conditions. Testing should intentionally attempt to make things go wrong to determine if things happen when they shouldn't or things don't happen when they should. It is oriented to 'detection'. (See the Bookstore section's 'Software Testing' category for a list of useful books on Software Testing.)
O2QYt;i0Organizations vary considerably in how they assign responsibility for QA and testing. Sometimes they're the combined responsibility of one group or individual. Also common are project teams that include a mix of testers and developers who work closely together, with overall QA processes monitored by project managers. It will depend on what best fits an organization's size and business structure.
4N-F3xl(d1a g!B(h$A0
o.F0@ gZ0K0y0Return to top of this page's FAQ list 51Testing软件测试网7a Y U_@/zF1n W
51Testing软件测试网 l yN Q1k{
What are some recent major computer system failures caused by software bugs?
1p\Yel G6`7a/In0Software problems in the automated baggage sorting system of a major airport in February 2008 prevented thousands of passengers from checking baggage for their flights. It was reported that the breakdown occurred during a software upgrade, despite pre-testing of the software. The system continued to have problems in subsequent months.
#O2x5ls|:Od1RD0News reports in December of 2007 indicated that significant software problems were continuing to occur in a new ERP payroll system for a large urban school system. It was believed that more than one third of employees had received incorrect paychecks at various times since the new system went live the preceding January, resulting in overpayments of $53 million, as well as underpayments. An employees' union brought a lawsuit against the school system, the cost of the ERP system was expected to rise by 40%, and the non-payroll part of the ERP system was delayed. Inadequate testing reportedly contributed to the problems. 51Testing软件测试网 RI?i Eg9}
In November of 2007 a regional government reportedly brought a multi-million dollar lawsuit against a software services vendor, claiming that the vendor 'minimized quality' in delivering software for a large criminal justice information system and the system did not meet requirements. The vendor also sued its subcontractor on the project. 51Testing软件测试网:S~KU s#K(a
In June of 2007 news reports claimed that software flaws in a popular online stock-picking contest could be used to gain an unfair advantage in pursuit of the game's large cash prizes. Outside investigators were called in and in July the contest winner was announced. Reportedly the winner had previously been in 6th place, indicating that the top 5 contestants may have been disqualified.
#] S ^2p#[U `9f4Uyh0A software problem contributed to a rail car fire in a major underground metro system in April of 2007 according to newspaper accounts. The software reportedly failed to perform as expected in detecting and preventing excess power usage in equipment on a new passenger rail car, resulting in overheating and fire in the rail car, and evacuation and shutdown of part of the system.
i[%x3O u0Tens of thousands of medical devices were recalled in March of 2007 to correct a software bug. According to news reports, the software would not reliably indicate when available power to the device was too low. 51Testing软件测试网9mc|~ [ Pm$E
A September 2006 news report indicated problems with software utilized in a state government's primary election, resulting in periodic unexpected rebooting of voter checkin machines, which were separate from the electronic voting machines, and resulted in confusion and delays at voting sites. The problem was reportedly due to insufficient testing. 51Testing软件测试网[%J0Hd{4j.kt x
In August of 2006 a U.S. government student loan service erroneously made public the personal data of as many as 21,000 borrowers on it's web site, due to a software error. The bug was fixed and the government department subsequently offered to arrange for free credit monitoring services for those affected. 51Testing软件测试网^1D3XK;B @q'M!W`
A software error reportedly resulted in overbilling of up to several thousand dollars to each of 11,000 customers of a major telecommunications company in June of 2006. It was reported that the software bug was fixed within days, but that correcting the billing errors would take much longer. 51Testing软件测试网 bP%{E3M6D6H `M
News reports in May of 2006 described a multi-million dollar lawsuit settlement paid by a healthcare software vendor to one of its customers. It was reported that the customer claimed there were problems with the software they had contracted for, including poor integration of software modules, and problems that resulted in missing or incorrect data used by medical personnel.
;Or|5z x;^@!m0In early 2006 problems in a government's financial monitoring software resulted in incorrect election candidate financial reports being made available to the public. The government's election finance reporting web site had to be shut down until the software was repaired.
3ZC:f7Z)N1c!h Cc5G0Trading on a major Asian stock exchange was brought to a halt in November of 2005, reportedly due to an error in a system software upgrade. The problem was rectified and trading resumed later the same day. 51Testing软件测试网[6x;n/m"M2B&\
A May 2005 newspaper article reported that a major hybrid car manufacturer had to install a software fix on 20,000 vehicles due to problems with invalid engine warning lights and occasional stalling. In the article, an automotive software specialist indicated that the automobile industry spends $2 billion to $3 billion per year fixing software problems.
3bG P7[M sw z+wE0Media reports in January of 2005 detailed severe problems with a $170 million high-profile U.S. government IT systems project. Software testing was one of the five major problem areas according to a report of the commission reviewing the project. In March of 2005 it was decided to scrap the entire project.
(^,e&tJi U$[N0In July 2004 newspapers reported that a new government welfare management system in Canada costing several hundred million dollars was unable to handle a simple benefits rate increase after being put into live operation. Reportedly the original contract allowed for only 6 weeks of acceptance testing and the system was never tested for its ability to handle a rate increase.
e7Y-['uvx4b+n,E0Millions of bank accounts were impacted by errors due to installation of inadequately tested software code in the transaction processing system of a major North American bank, according to mid-2004 news reports. Articles about the incident stated that it took two weeks to fix all the resulting errors, that additional problems resulted when the incident drew a large number of e-mail phishing attacks against the bank's customers, and that the total cost of the incident could exceed $100 million. 51Testing软件测试网N&_+AY;I O4X*XI
A bug in site management software utilized by companies with a significant percentage of worldwide web traffic was reported in May of 2004. The bug resulted in performance problems for many of the sites simultaneously and required disabling of the software until the bug was fixed.
0`&dZ qKIIx0According to news reports in April of 2004, a software bug was determined to be a major contributor to the 2003 Northeast blackout, the worst power system failure in North American history. The failure involved loss of electrical power to 50 million customers, forced shutdown of 100 power plants, and economic losses estimated at $6 billion. The bug was reportedly in one utility company's vendor-supplied power monitoring and management system, which was unable to correctly handle and report on an unusual confluence of initially localized events. The error was found and corrected after examining millions of lines of code. 51Testing软件测试网N[ {{_1b%nG}
In early 2004, news reports revealed the intentional use of a software bug as a counter-espionage tool. According to the report, in the early 1980's one nation surreptitiously allowed a hostile nation's espionage service to steal a version of sophisticated industrial software that had intentionally-added flaws. This eventually resulted in major industrial disruption in the country that used the stolen flawed software. 51Testing软件测试网Fx!B)vUZ T
A major U.S. retailer was reportedly hit with a large government fine in October of 2003 due to web site errors that enabled customers to view one anothers' online orders. 51Testing软件测试网'qfNbo}
News stories in the fall of 2003 stated that a manufacturing company recalled all their transportation products in order to fix a software problem causing instability in certain circumstances. The company found and reported the bug itself and initiated the recall procedure in which a software upgrade fixed the problems.
cM1|*yk6H5b0In August of 2003 a U.S. court ruled that a lawsuit against a large online brokerage company could proceed; the lawsuit reportedly involved claims that the company was not fixing system problems that sometimes resulted in failed stock trades, based on the experiences of 4 plaintiffs during an 8-month period. A previous lower court's ruling that "...six miscues out of more than 400 trades does not indicate negligence." was invalidated.
?P P5jw&]0In April of 2003 it was announced that a large student loan company in the U.S. made a software error in calculating the monthly payments on 800,000 loans. Although borrowers were to be notified of an increase in their required payments, the company will still reportedly lose $8 million in interest. The error was uncovered when borrowers began reporting inconsistencies in their bills.
t)@|GB0News reports in February of 2003 revealed that the U.S. Treasury Department mailed 50,000 Social Security checks without any beneficiary names. A spokesperson indicated that the missing names were due to an error in a software change. Replacement checks were subsequently mailed out with the problem corrected, and recipients were then able to cash their Social Security checks.
#K FhH*c Y}5Y0In March of 2002 it was reported that software bugs in Britain's national tax system resulted in more than 100,000 erroneous tax overcharges. The problem was partly attributed to the difficulty of testing the integration of multiple systems. 51Testing软件测试网:fKg F(S q JM2A!^
A newspaper columnist reported in July 2001 that a serious flaw was found in off-the-shelf software that had long been used in systems for tracking certain U.S. nuclear materials. The same software had been recently donated to another country to be used in tracking their own nuclear materials, and it was not until scientists in that country discovered the problem, and shared the information, that U.S. officials became aware of the problems. 51Testing软件测试网/A` @yHn
According to newspaper stories in mid-2001, a major systems development contractor was fired and sued over problems with a large retirement plan management system. According to the reports, the client claimed that system deliveries were late, the software had excessive defects, and it caused other systems to crash.
!p Td:n }2~0In January of 2001 newspapers reported that a major European railroad was hit by the aftereffects of the Y2K bug. The company found that many of their newer trains would not run due to their inability to recognize the date '31/12/2000'; the trains were started by altering the control system's date settings.
J xH3I&z(^6l0News reports in September of 2000 told of a software vendor settling a lawsuit with a large mortgage lender; the vendor had reportedly delivered an online mortgage processing system that did not meet specifications, was delivered late, and didn't work. 51Testing软件测试网4h*c UP8r's,s
In early 2000, major problems were reported with a new computer system in a large suburban U.S. public school district with 100,000+ students; problems included 10,000 erroneous report cards and students left stranded by failed class registration systems; the district's CIO was fired. The school district decided to reinstate it's original 25-year old system for at least a year until the bugs were worked out of the new system by the software vendors. 51Testing软件测试网z/RTvB{ty'~
A review board concluded that the NASA Mars Polar Lander failed in December 1999 due to software problems that caused improper functioning of retro rockets utilized by the Lander as it entered the Martian atmosphere. 51Testing软件测试网 w(~7la%T`,P(WZX
In October of 1999 the $125 million NASA Mars Climate Orbiter spacecraft was believed to be lost in space due to a simple data conversion error. It was determined that spacecraft software used certain data in English units that should have been in metric units. Among other tasks, the orbiter was to serve as a communications relay for the Mars Polar Lander mission, which failed for unknown reasons in December 1999. Several investigating panels were convened to determine the process failures that allowed the error to go undetected. 51Testing软件测试网 KIK B*H7Xf)GN
Bugs in software supporting a large commercial high-speed data network affected 70,000 business customers over a period of 8 days in August of 1999. Among those affected was the electronic trading system of the largest U.S. futures exchange, which was shut down for most of a week as a result of the outages. 51Testing软件测试网x8v H2TE
In April of 1999 a software bug caused the failure of a $1.2 billion U.S. military satellite launch, the costliest unmanned accident in the history of Cape Canaveral launches. The failure was the latest in a string of launch failures, triggering a complete military and industry review of U.S. space launch programs, including software integration and testing processes. Congressional oversight hearings were requested. 51Testing软件测试网.V eG _S+y
A small town in Illinois in the U.S. received an unusually large monthly electric bill of $7 million in March of 1999. This was about 700 times larger than its normal bill. It turned out to be due to bugs in new software that had been purchased by the local power company to deal with Y2K software issues. 51Testing软件测试网)rqx l5v T,q P a q@
In early 1999 a major computer game company recalled all copies of a popular new product due to software problems. The company made a public apology for releasing a product before it was ready.
P0G8` mT1[0The computer system of a major online U.S. stock trading service failed during trading hours several times over a period of days in February of 1999 according to nationwide news reports. The problem was reportedly due to bugs in a software upgrade intended to speed online trade confirmations.
(S [,j/fe-U L0In April of 1998 a major U.S. data communications network failed for 24 hours, crippling a large part of some U.S. credit card transaction authorization systems as well as other large U.S. bank, retail, and government data systems. The cause was eventually traced to a software bug.
uUBT H ET0January 1998 news reports told of software problems at a major U.S. telecommunications company that resulted in no charges for long distance calls for a month for 400,000 customers. The problem went undetected until customers called up with questions about their bills. 51Testing软件测试网6X[ _;W0Q0B
In November of 1997 the stock of a major health industry company dropped 60% due to reports of failures in computer billing systems, problems with a large database conversion, and inadequate software testing. It was reported that more than $100,000,000 in receivables had to be written off and that multi-million dollar fines were levied on the company by government agencies.
C+[({&p e"~0A retail store chain filed suit in August of 1997 against a transaction processing system vendor (not a credit card company) due to the software's inability to handle credit cards with year 2000 expiration dates.
3w.W9I1B g0P+C}!E!O0In August of 1997 one of the leading consumer credit reporting companies reportedly shut down their new public web site after less than two days of operation due to software problems. The new site allowed web site visitors instant access, for a small fee, to their personal credit reports. However, a number of initial users ended up viewing each others' reports instead of their own, resulting in irate customers and nationwide publicity. The problem was attributed to "...unexpectedly high demand from consumers and faulty software that routed the files to the wrong computers."
_t g.fh I+z/u [0In November of 1996, newspapers reported that software bugs caused the 411 telephone information system of one of the U.S. RBOC's to fail for most of a day. Most of the 2000 operators had to search through phone books instead of using their 13,000,000-listing database. The bugs were introduced by new software modifications and the problem software had been installed on both the production and backup systems. A spokesman for the software vendor reportedly stated that 'It had nothing to do with the integrity of the software. It was human error.' 51Testing软件测试网h;\4r7i3[ J6R/~;@
On June 4 1996 the first flight of the European Space Agency's new Ariane 5 rocket failed shortly after launching, resulting in an estimated uninsured loss of a half billion dollars. It was reportedly due to the lack of exception handling of a floating-point error in a conversion from a 64-bit integer to a 16-bit signed integer.
.D~gX;b E ~0Software bugs caused the bank accounts of 823 customers of a major U.S. bank to be credited with $924,844,208.32 each in May of 1996, according to newspaper reports. The American Bankers Association claimed it was the largest such error in banking history. A bank spokesman said the programming errors were corrected and all funds were recovered. 51Testing软件测试网n D$|:k0ZS c
On January 1 1984 all computers produced by one of the leading minicomputer makers of the time reportedly failed worldwide. The cause was claimed to be a leap year bug in a date handling function utilized in deletion of temporary operating system files. Technicians throughout the world worked for several days to clear up the problem. It was also reported that the same bug affected many of the same computers four years later.
Pr"pA H4K Fb sG0Software bugs in a Soviet early-warning monitoring system nearly brought on nuclear war in 1983, according to news reports in early 1999. The software was supposed to filter out false missile detections caused by Soviet satellites picking up sunlight reflections off cloud-tops, but failed to do so. Disaster was averted when a Soviet commander, based on what he said was a '...funny feeling in my gut', decided the apparent missile attack was a false alarm. The filtering software code was rewritten.
0^&| y9z%KO@%dX0
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|M!N _W0
n f+q)y y:p oDF8C F |0Does every software project need testers? 51Testing软件测试网l'MDX }
While all projects will benefit from testing, some projects may not require independent test staff to succeed. 51Testing软件测试网wc3B&H U/|q y
51Testing软件测试网 e(LR$s2^5w8C q
Which projects may not need independent test staff? The answer depends on the size and context of the project, the risks, the development methodology, the skill and experience of the developers, and other factors. For instance, if the project is a short-term, small, low risk project, with highly experienced programmers utilizing thorough unit testing or test-first development, then test engineers may not be required for the project to succeed.
/i k}&UP1P-vA051Testing软件测试网1X7c F Q&g"Q r;~$r
In some cases an IT organization may be too small or new to have a testing staff even if the situation calls for it. In these circumstances it may be appropriate to instead use contractors or outsourcing, or adjust the project management and development approach (by switching to more senior developers and agile test-first development, for example). Inexperienced managers sometimes gamble on the success of a project by skipping thorough testing or having programmers do post-development functional testing of their own work, a decidedly high risk gamble.
-K8}+q1SINLm }%q051Testing软件测试网4O L[l%^1@b T)\ OF
For non-trivial-size projects or projects with non-trivial risks, a testing staff is usually necessary. As in any business, the use of personnel with specialized skills enhances an organization's ability to be successful in large, complex, or difficult tasks. It allows for both a) deeper and stronger skills and b) the contribution of differing perspectives. For example, programmers typically have the perspective of 'what are the technical issues in making this functionality work?'. A test engineer typically has the perspective of 'what might go wrong with this functionality, and how can we ensure it meets expectations?'. Technical people who can be highly effective in approaching tasks from both of those perspectives are rare, which is why, sooner or later, organizations bring in test specialists. 51Testing软件测试网7L){ L F^!a5B
51Testing软件测试网.r'KIp ]'H.b3_"E
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.Z X\ V8eV0Why does software have bugs?
E#vaz;@0miscommunication or no communication - as to specifics of what an application should or shouldn't do (the application's requirements). 51Testing软件测试网0P8l(_%Z'q I5D-u
software complexity - the complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development. Multi-tier distributed systems, applications utilizing mutliple local and remote web services applications, data communications, enormous relational databases, security complexities, and sheer size of applications have all contributed to the exponential growth in software/system complexity.
P^1M[ R)S1W0programming errors - programmers, like anyone else, can make mistakes.
$^,e(n#y G U0changing requirements (whether documented or undocumented) - the end-user may not understand the effects of changes, or may understand and request them anyway - redesign, rescheduling of engineers, effects on other projects, work already completed that may have to be redone or thrown out, hardware requirements that may be affected, etc. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of coordinating changes may result in errors. Enthusiasm of engineering staff may be affected. In some fast-changing business environments, continuously modified requirements may be a fact of life. In this case, management must understand the resulting risks, and QA and test engineers must adapt and plan for continuous extensive testing to keep the inevitable bugs from running out of control - see 'What can be done if requirements are changing continuously?' in the LFAQ. Also see information about 'agile' approaches such as XP, in Part 2 of the FAQ. 51Testing软件测试网+OP"[8J$|:V An5F
time pressures - scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.
hc j3EWE#Y0egos - people prefer to say things like:
7Rh {:zwkwC\0 'no problem'
X jSC px:i RK"Mr0 'piece of cake'51Testing软件测试网(FH*M$WO%MF8L\
'I can whip that out in a few hours'
.g-`\| ]+f0 'it should be easy to update that old code'51Testing软件测试网+G~!bF!~S
~ IH0q W3Yj9y0 instead of:51Testing软件测试网 ciA)l3U2s fX9r
'that adds a lot of complexity and we could end up51Testing软件测试网6UF1fQP*a0W
making a lot of mistakes'
-d Ot1at3I6F2L |(d Y0 'we have no idea if we can do that; we'll wing it'51Testing软件测试网8m5ey(hp$D t C @
'I can't estimate how long it will take, until I51Testing软件测试网UVT V5W {^0M
take a close look at it'
&g ~D_!K b-X0 'we can't figure out what that old spaghetti code51Testing软件测试网Bvj'll*T
did in the first place'51Testing软件测试网;I _9x.KXA
k*g [+H*H'q0 If there are too many unrealistic 'no problem's', the
ol mCh?6LE&C]0 result is bugs.51Testing软件测试网0L'`"H+u}+ox&W
51Testing软件测试网$G z @2w A#F:g
poorly documented code - it's tough to maintain and modify code that is badly written or poorly documented; the result is bugs. In many organizations management provides no incentive for programmers to document their code or write clear, understandable, maintainable code. In fact, it's usually the opposite: they get points mostly for quickly turning out code, and there's job security if nobody else can understand it ('if it was hard to write, it should be hard to read'). 51Testing软件测试网 U'^x6lB?;a$p
software development tools - visual tools, class libraries, compilers, scrīpting tools, etc. often introduce their own bugs or are poorly documented, resulting in added bugs.
1e+}'H3Z2w l$I0
I D"z6eF"s8_0Return to top of this page's FAQ list 51Testing软件测试网 Z,O/OCF8i {[ v
51Testing软件测试网(p%e{1KP8?-x
How can new Software QA processes be introduced in an existing organization? 51Testing软件测试网 ?7?:mT gu F
A lot depends on the size of the organization and the risks involved. For large organizations with high-risk (in terms of lives or property) projects, serious management buy-in is required and a formalized QA process is necessary. 51Testing软件测试网(M({ U2gK,m om
Where the risk is lower, management and organizational buy-in and QA implementation may be a slower, step-at-a-time process. QA processes should be balanced with productivity so as to keep bureaucracy from getting out of hand. 51Testing软件测试网YC$@d V%FP#M
For small groups or projects, a more ad-hoc process may be appropriate, depending on the type of customers and projects. A lot will depend on team leads or managers, feedback to developers, and ensuring adequate communications among customers, managers, developers, and testers. 51Testing软件测试网+||E Y:G,{%M-f b+_
The most value for effort will often be in (a) requirements management processes, with a goal of clear, complete, testable requirement specifications embodied in requirements or design documentation, or in 'agile'-type environments extensive continuous coordination with end-users, (b) design inspections and code inspections, and (c) post-mortems/retrospectives. 51Testing软件测试网T `Vs%t
Other possibilities include incremental self-managed team approaches such as 'Kaizen' methods of continuous process improvement, the Deming-Shewhart Plan-Do-Check-Act cycle, and others. 51Testing软件测试网GZ!iT J:t
Also see 'How can QA processes be implemented without reducing productivity?' in the LFAQ section.
sB.]rB4[Y0
kA/Xx'wEL/JU0(See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.) 51Testing软件测试网o)z {+^ X4n9V
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2B4ZZM aX3U `m0What is verification? validation? 51Testing软件测试网*U i2T o YhkW P
Verification typically involves reviews and meetings to evaluate documents, plans, code, requirements, and specifications. This can be done with checklists, issues lists, walkthroughs, and inspection meetings. Validation typically involves actual testing and takes place after verifications are completed. The term 'IV & V' refers to Independent Verification and Validation.
i2R Y1CGZ~/`051Testing软件测试网$D'\*~ r ]s
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"]/V ~%JJ(f0
|/f*Jh'o D0M @|!le0What is a 'walkthrough'? 51Testing软件测试网#n0H:nq|(`0ra
A 'walkthrough' is an informal meeting for evaluation or informational purposes. Little or no preparation is usually required. 51Testing软件测试网6T#MN L)r(c
s)OAc RO0Return to top of this page's FAQ list 51Testing软件测试网ym*Q+S6~*pL
51Testing软件测试网\.W\/g.oPbF
What's an 'inspection'?
R{w*V2V#\0An inspection is more formalized than a 'walkthrough', typically with 3-8 people including a moderator, reader, and a recorder to take notes. The subject of the inspection is typically a document such as a requirements spec or a test plan, and the purpose is to find problems and see what's missing, not to fix anything. Attendees should prepare for this type of meeting by reading thru the document; most problems will be found during this preparation. The result of the inspection meeting should be a written report. Thorough preparation for inspections is difficult, painstaking work, but is one of the most cost effective methods of ensuring quality. Employees who are most skilled at inspections are like the 'eldest brother' in the parable in 'Why is it often hard for organizations to get serious about quality assurance?'. Their skill may have low visibility but they are extremely valuable to any software development organization, since bug prevention is far more cost-effective than bug detection. 51Testing软件测试网#MX$| x&N {e
51Testing软件测试网 b4ON-{4E D _
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Si[v7n5^/O$@!q051Testing软件测试网*j xB$UOG9A"Am4Q
What kinds of testing should be considered? 51Testing软件测试网9`lhE F^d@
Black box testing - not based on any knowledge of internal design or code. Tests are based on requirements and functionality. 51Testing软件测试网(@:H5t L#X8q @U4v%m
White box testing - based on knowledge of the internal logic of an application's code. Tests are based on coverage of code statements, branches, paths, conditions. 51Testing软件测试网g _ Z [1jk~8j
unit testing - the most 'micro' scale of testing; to test particular functions or code modules. Typically done by the programmer and not by testers, as it requires detailed knowledge of the internal program design and code. Not always easily done unless the application has a well-designed architecture with tight code; may require developing test driver modules or test harnesses. 51Testing软件测试网,Gq'[._ U z3R#J1E
incremental integration testing - continuous testing of an application as new functionality is added; requires that various aspects of an application's functionality be independent enough to work separately before all parts of the program are completed, or that test drivers be developed as needed; done by programmers or by testers. 51Testing软件测试网J0Q W3Fti
integration testing - testing of combined parts of an application to determine if they function together correctly. The 'parts' can be code modules, individual applications, client and server applications on a network, etc. This type of testing is especially relevant to client/server and distributed systems. 51Testing软件测试网 FL$pgE;R
functional testing - black-box type testing geared to functional requirements of an application; this type of testing should be done by testers. This doesn't mean that the programmers shouldn't check that their code works before releasing it (which of course applies to any stage of testing.) 51Testing软件测试网3u RL+w6[0pO
system testing - black-box type testing that is based on overall requirements specifications; covers all combined parts of a system. 51Testing软件测试网(Y9l O tt"V x9g0f-?
end-to-end testing - similar to system testing; the 'macro' end of the test scale; involves testing of a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.
"k `F!j*}n0sanity testing or smoke testing - typically an initial testing effort to determine if a new software version is performing well enough to accept it for a major testing effort. For example, if the new software is crashing systems every 5 minutes, bogging down systems to a crawl, or corrupting databases, the software may not be in a 'sane' enough condition to warrant further testing in its current state.
Ui(U:B4C:F Y`7S0regression testing - re-testing after fixes or modifications of the software or its environment. It can be difficult to determine how much re-testing is needed, especially near the end of the development cycle. Automated testing tools can be especially useful for this type of testing.
._+c xi-v&e0acceptance testing - final testing based on specifications of the end-user or customer, or based on use by end-users/customers over some limited period of time. 51Testing软件测试网 zF5Jl9I X
load testing - testing an application under heavy loads, such as testing of a web site under a range of loads to determine at what point the system's response time degrades or fails.
^&\9b2M1{0stress testing - term often used interchangeably with 'load' and 'performance' testing. Also used to describe such tests as system functional testing while under unusually heavy loads, heavy repetition of certain actions or inputs, input of large numerical values, large complex queries to a database system, etc.
X2n#\ { WOJ0performance testing - term often used interchangeably with 'stress' and 'load' testing. Ideally 'performance' testing (and any other 'type' of testing) is defined in requirements documentation or QA or Test Plans.
:m | sP;yu0usability testing - testing for 'user-friendliness'. Clearly this is subjective, and will depend on the targeted end-user or customer. User interviews, surveys, video recording of user sessions, and other techniques can be used. Programmers and testers are usually not appropriate as usability testers.
C)weFIsT b0install/uninstall testing - testing of full, partial, or upgrade install/uninstall processes. 51Testing软件测试网h1^6P|Of T7Z$F
recovery testing - testing how well a system recovers from crashes, hardware failures, or other catastrophic problems.
'[4Y u!\;j+Q@0failover testing - typically used interchangeably with 'recovery testing' 51Testing软件测试网X+hD7K4ql,n k |
security testing - testing how well the system protects against unauthorized internal or external access, willful damage, etc; may require sophisticated testing techniques.
/C F-t:R x6zs"{0compatability testing - testing how well software performs in a particular hardware/software/operating system/network/etc. environment. 51Testing软件测试网:I$}`5G(H7y1w
exploratory testing - often taken to mean a creative, informal software test that is not based on formal test plans or test cases; testers may be learning the software as they test it. 51Testing软件测试网u? g n U5I
ad-hoc testing - similar to exploratory testing, but often taken to mean that the testers have significant understanding of the software before testing it. 51Testing软件测试网(f BAs J LB!C l a
context-driven testing - testing driven by an understanding of the environment, culture, and intended use of software. For example, the testing approach for life-critical medical equipment software would be completely different than that for a low-cost computer game.
.wh\`:E0i\\R| u0user acceptance testing - determining if software is satisfactory to an end-user or customer. 51Testing软件测试网H k"pQ Z/V L+C b0`:g;?
comparison testing - comparing software weaknesses and strengths to competing products.
0r;Z`2w"Ku N/Q0alpha testing - testing of an application when development is nearing completion; minor design changes may still be made as a result of such testing. Typically done by end-users or others, not by programmers or testers.
@*}"k mT ~Ec%G0beta testing - testing when development and testing are essentially completed and final bugs and problems need to be found before final release. Typically done by end-users or others, not by programmers or testers. 51Testing软件测试网"}6y v!]f3^%jM @
mutation testing - a method for determining if a set of test data or test cases is useful, by deliberately introducing various code changes ('bugs') and retesting with the original test data/cases to determine if the 'bugs' are detected. Proper implementation requires large computational resources.
9Z n"y1A1o i0(See the Bookstore section's 'Software Testing' category for useful books on Software Testing.) 51Testing软件测试网9l.V3A)t4k [8j9l5c
51Testing软件测试网:K'T4He+WB ]
Return to top of this page's FAQ list 51Testing软件测试网8_r)g U @/dt
51Testing软件测试网8?-da3w&OB/N
What are 5 common problems in the software development process?
:yI6VX q0poor requirements - if requirements are unclear, incomplete, too general, and not testable, there will be problems. 51Testing软件测试网+u.Z? n$L y8]\
unrealistic schedule - if too much work is crammed in too little time, problems are inevitable.
@]$R C)];U0inadequate testing - no one will know whether or not the program is any good until the customer complains or systems crash.
{j4g&D3O2vH0featuritis - requests to pile on new features after development is underway; extremely common. 51Testing软件测试网1cFy[.|`.C3yKF
miscommunication - if developers don't know what's needed or customer's have erroneous expectations, problems can be expected.
a XBj$E%@9}#a3?r0(See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.) 51Testing软件测试网.x#_$].hay4k {
%U4b(Dad.Q @W0Return to top of this page's FAQ list 51Testing软件测试网i3u3M+z3Y s,D){
51Testing软件测试网d [b Aa$X2n~
What are 5 common solutions to software development problems?
uLA2@CD ]6ns0solid requirements - clear, complete, detailed, cohesive, attainable, testable requirements that are agreed to by all players. In 'agile'-type environments, continuous close coordination with customers/end-users is necessary to ensure that changing/emerging requirements are understood.
4p9l \!uy(O9U9C0realistic schedules - allow adequate time for planning, design, testing, bug fixing, re-testing, changes, and documentation; personnel should be able to complete the project without burning out.
dqib @$`x%~Z0adequate testing - start testing early on, re-test after fixes or changes, plan for adequate time for testing and bug-fixing. 'Early' testing could include static code analysis/testing, test-first development, unit testing by developers, built-in testing and diagnostic capabilities, automated post-build testing, etc. 51Testing软件测试网t4T2t'^lF0D:{b
stick to initial requirements where feasible - be prepared to defend against excessive changes and additions once development has begun, and be prepared to explain consequences. If changes are necessary, they should be adequately reflected in related schedule changes. If possible, work closely with customers/end-users to manage expectations. In 'agile'-type environments, initial requirements may be expected to change significantly, requiring that true agile processes be in place. 51Testing软件测试网 y2mT.U x(Ia5np
communication - require walkthroughs and inspections when appropriate; make extensive use of group communication tools - groupware, wiki's, bug-tracking tools and change management tools, intranet capabilities, etc.; ensure that information/documentation is available and up-to-date - preferably electronic, not paper; promote teamwork and cooperation; use protoypes and/or continuous communication with end-users if possible to clarify expectations. 51Testing软件测试网.e5If5M)d V j9F5v6hf7?
(See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.) 51Testing软件测试网,v2I|5?j ~
2~2Eh&Rdf0Return to top of this page's FAQ list 51Testing软件测试网+@4y^$D`t^,y
"U$J jg:^ Nl6tY{2?#@0What is software 'quality'? 51Testing软件测试网6Tw(V3aO {!}b {
Quality software is reasonably bug-free, delivered on time and within budget, meets requirements and/or expectations, and is maintainable. However, quality is obviously a subjective term. It will depend on who the 'customer' is and their overall influence in the scheme of things. A wide-angle view of the 'customers' of a software development project might include end-users, customer acceptance testers, customer contract officers, customer management, the development organization's management/accountants/testers/salespeople, future software maintenance engineers, stockholders, magazine columnists, etc. Each type of 'customer' will have their own slant on 'quality' - the accounting department might define quality in terms of profits while an end-user might define quality as user-friendly and bug-free. (See the Bookstore section's 'Software QA' category for useful books with more information.) 51Testing软件测试网 gM f*~ `
1f4L H Q8P2k0Return to top of this page's FAQ list 51Testing软件测试网1\X.u8A7U-MI p0PE
X mJ7k3@ C b7p k0What is 'good code'?
)D UC*gg;du$A M0'Good code' is code that works, is reasonably bug free, and is readable and maintainable. Some organizations have coding 'standards' that all developers are supposed to adhere to, but everyone has different ideas about what's best, or what is too many or too few rules. There are also various theories and metrics, such as McCabe Complexity metrics. It should be kept in mind that excessive use of standards and rules can stifle productivity and creativity. 'Peer reviews', 'buddy checks' pair programming, code analysis tools, etc. can be used to check for problems and enforce standards.
z#^ cq m2NFY9tJED0For example, in C/C++ coding, here are some typical ideas to consider in setting rules/standards; these may or may not apply to a particular situation:
A1_+G1TFIq0minimize or eliminate use of global variables. 51Testing软件测试网*w U cX&U J
use descrīptive function and method names - use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descrīptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
V"a#uPqfc0use descrīptive variable names - use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descrīptive (use of more than 20 characters is not out of line); be consistent in naming conventions. 51Testing软件测试网6X Y#n!CS
function and method sizes should be minimized; less than 100 lines of code is good, less than 50 lines is preferable. 51Testing软件测试网SMFm.iN X-g4_+W
function descrīptions should be clearly spelled out in comments preceding a function's code.
)B~EiS0organize code for readability. 51Testing软件测试网&M ngkd"d@
use whitespace generously - vertically and horizontally 51Testing软件测试网2? j1U U@
each line of code should contain 70 characters max. 51Testing软件测试网P'vd*pWV;@
one code statement per line.
x F ACz(n%a0coding style should be consistent throught a program (eg, use of brackets, indentations, naming conventions, etc.)
XJ)eJE d3i4V0in adding comments, err on the side of too many rather than too few comments; a common rule of thumb is that there should be at least as many lines of comments (including header blocks) as lines of code.
A7AA#do'\Zj4e$R0no matter how small, an application should include documentaion of the overall program function and flow (even a few paragraphs is better than nothing); or if possible a separate flow chart and detailed program documentation. 51Testing软件测试网 G!j~-Q;m aw
make extensive use of error handling procedures and status and error logging. 51Testing软件测试网a/p p X*Rw
for C++, to minimize complexity and increase maintainability, avoid too many levels of inheritance in class heirarchies (relative to the size and complexity of the application). Minimize use of multiple inheritance, and minimize use of operator overloading (note that the Java programming language eliminates multiple inheritance and operator overloading.) 51Testing软件测试网 G `(T0}V9^#c d{8[L
for C++, keep class methods small, less than 50 lines of code per method is preferable.
`h]"XvL now0for C++, make liberal use of exception handlers 51Testing软件测试网 U5v c0cJ*_
!D ^5P3e3Y6U,] }0Return to top of this page's FAQ list 51Testing软件测试网E LD.v x||:~Y
51Testing软件测试网%l ID6_)o/R?
What is 'good design'? 51Testing软件测试网H;KH0|`5bp&e%Dk
'Design' could refer to many things, but often refers to 'functional design' or 'internal design'. Good internal design is indicated by software code whose overall structure is clear, understandable, easily modifiable, and maintainable; is robust with sufficient error-handling and status logging capability; and works correctly when implemented. Good functional design is indicated by an application whose functionality can be traced back to customer and end-user requirements. (See further discussion of functional and internal design in 'What's the big deal about requirements?' in FAQ #2.) For programs that have a user interface, it's often a good idea to assume that the end user will have little computer knowledge and may not read a user manual or even the on-line help; some common rules-of-thumb include:
UY'?6F0F0W$Y0the program should act in a way that least surprises the user 51Testing软件测试网%x MuMt*ny8O:}
it should always be evident to the user what can be done next and how to exit 51Testing软件测试网NxoP-b Mc:w(d
the program shouldn't let the users do something stupid without warning them.
(d?Li3b"[051Testing软件测试网)C{,vX8?:o2aSb
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*j3\F o _ F~9H d|+l2P0What is SEI? CMM? CMMI? ISO? IEEE? ANSI? Will it help?
+}?P{&Y E ~.{0SEI = 'Software Engineering Institute' at Carnegie-Mellon University; initiated by the U.S. Defense Department to help improve software development processes.
I%|?"~_$MW0CMM = 'Capability Maturity Model', now called the CMMI ('Capability Maturity Model Integration'), developed by the SEI. It's a model of 5 levels of process 'maturity' that determine effectiveness in delivering quality software. It is geared to large organizations such as large U.S. Defense Department contractors. However, many of the QA processes involved are appropriate to any organization, and if reasonably applied can be helpful. Organizations can receive CMMI ratings by undergoing assessments by qualified auditors.
2tG)H d:v&}.yt E0 Level 1 - characterized by chaos, periodic panics, and heroic51Testing软件测试网 a#q(UK1F4hb#Q6m'M
efforts required by individuals to successfully51Testing软件测试网2x0j] }!},m A#X.s {E
complete projects. Few if any processes in place;
;fF x5lS+w7@ f.FF0 successes may not be repeatable.
.S n q3[W(IX6rhcjp5{051Testing软件测试网M:Rr Vd1OT8q
Level 2 - software project tracking, requirements management,51Testing软件测试网@X8s*r$Z0O8i
realistic planning, and configuration management
H9U;Ip;U2@f0 processes are in place; successful practices can
'F(_%b @$x9G;l0 be repeated.51Testing软件测试网oLJ vVS5]*?[
q}m|%r1R C1Fj0 Level 3 - standard software development and maintenance processes
4L;d6E&H k$_:A0 are integrated throughout an organization; a Software
vn1l `Gw@ b5c*@0 Engineering Process Group is is in place to oversee51Testing软件测试网-X.tQ9v/Ur.|
software processes, and training programs are used to
.F2X#DH6Su+J(m0 ensure understanding and compliance.51Testing软件测试网XE4B:\n
#f2G t.UV1T0 Level 4 - metrics are used to track productivity, processes,51Testing软件测试网/i~Bn [1I$~bc
and products. Project performance is predictable,51Testing软件测试网 z!w"T PY%y d8? B X
and quality is consistently high.
4KR'z2y"bcY9y051Testing软件测试网f(I5[s'd U d
Level 5 - the focus is on continouous process improvement. The
q$eJ*P1}+j`0 impact of new processes and technologies can be
;P(F7I~~id S0 predicted and effectively implemented when required.51Testing软件测试网r)P n3J.Q'p G Cl4d\
b+kN!q En k0
1aB v/Z&K'@*F%s0 Perspective on CMM ratings: During 1997-2001, 1018 organizations51Testing软件测试网+|d)v_[(r&o Z
were assessed. Of those, 27% were rated at Level 1, 39% at 2,51Testing软件测试网.A0i7b dA
23% at 3, 6% at 4, and 5% at 5. (For ratings during the period 51Testing软件测试网$X$i B)n iM'K
1992-96, 62% were at Level 1, 23% at 2, 13% at 3, 2% at 4, and 51Testing软件测试网2@EH#N,N$|
0.4% at 5.) The median size of organizations was 100 software
E7{4aY_ nM0 engineering/maintenance personnel; 32% of organizations were
,` I+W)^0\5n xM0 U.S. federal contractors or agencies. For those rated at
2C{2s z Mq9fT0 Level 1, the most problematical key process area was in
P0J^(gX^bVH0 Software Quality Assurance.51Testing软件测试网2d9} BiH
NiG j ` [ XD/^0ISO = 'International Organisation for Standardization' - The ISO 9001:2000 standard (which replaces the previous standard of 1994) concerns quality systems that are assessed by outside auditors, and it applies to many kinds of production and manufacturing organizations, not just software. It covers documentation, design, development, production, testing, installation, servicing, and other processes. The full set of standards consists of: (a)Q9001-2000 - Quality Management Systems: Requirements; (b)Q9000-2000 - Quality Management Systems: Fundamentals and Vocabulary; (c)Q9004-2000 - Quality Management Systems: Guidelines for Performance Improvements. To be ISO 9001 certified, a third-party auditor assesses an organization, and certification is typically good for about 3 years, after which a complete reassessment is required. Note that ISO certification does not necessarily indicate quality products - it indicates only that documented processes are followed. Also see http://www.iso.org/ for the latest information. In the U.S. the standards can be purchased via the ASQ web site at http://www.asq.org/quality-press/ 51Testing软件测试网 LZ%]0X$H:uq v
ISO 9126 defines six high level quality characteristics that can be used in software evaluation. It includes functionality, reliability, usability, efficiency, maintainability, and portability.
] u_5V%b/} ]0IEEE = 'Institute of Electrical and Electronics Engineers' - among other things, creates standards such as 'IEEE Standard for Software Test Documentation' (IEEE/ANSI Standard 829), 'IEEE Standard of Software Unit Testing (IEEE/ANSI Standard 1008), 'IEEE Standard for Software Quality Assurance Plans' (IEEE/ANSI Standard 730), and others.
3C;s*P0L}1@0ANSI = 'American National Standards Institute', the primary industrial standards body in the U.S.; publishes some software-related standards in conjunction with the IEEE and ASQ (American Society for Quality).
@|*y8B3i!X$J}"v"MN0Other software development/IT management process assessment methods besides CMMI and ISO 9000 include SPICE, Trillium, TickIT, Bootstrap, ITIL, MOF, and CobiT. 51Testing软件测试网 N HH!U Iu$Z f,o3\
See the 'Other Resources' section for further information available on the web.
;G Y ? a ?y1n/h+f8_051Testing软件测试网@ U[0F2\
Return to top of this page's FAQ list 51Testing软件测试网 d }Q B `ql%Dv
.[ hP } Z'L9j0What is the 'software life cycle'? 51Testing软件测试网 kB7q+Qmvt W D Q
The life cycle begins when an application is first conceived and ends when it is no longer in use. It includes aspects such as initial concept, requirements analysis, functional design, internal design, documentation planning, test planning, coding, document preparation, integration, testing, maintenance, updates, retesting, phase-out, and other aspects. (See the Bookstore section's 'Software QA', 'Software Engineering', and 'Project Management' categories for useful books with more information.)
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相关阅读:
- what is a bug? (wxf_xsfy, 2008-8-21)
- What is "Software Testing Life Cycle"? (wxf_xsfy, 2008-8-22)
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